Rotary fluid actuator



Nov. 15, 1960 A. P. HENRY ROTARY FLUID ACTUATOR Filed June 9, 1958 2 Sheets-Sheet 1 BY g Nov. l5, 1960 A. P. HENRY 2,960,076

ROTARY FLUID AcTuAToR Filed June 9, 1958 Y 2 sneetsfsheet 2 ROTARY 'FLUID ACTUATOR Augustus P. Henry, 1127 Berkshire Lane, Newport Beach, Calif.

Filed June 9, 1958, Ser. No. 740,918

Claims. (Cl. 121-99) This invention relates generally to fluid powered rnc tors, and more particularly to improvements in rotary fluid actuators.

A typical rotary iluid actuator consists of an outer housing or stator` and an inner rotor which operates in a generally cylindrical bore in the stator. This rotor includes a central shaft or body which is concentric with and radially spaced from the wall of the stator bore.

Extending radially outward from the rotor body and radially inward from the wall of the stator bore are vanelike projections. The radial projections on the rotor will be hereinafter referred to as movable vanes, while those on the stator will be referred to as stationary vanes.

These vanes extend across the annular space between the rotor body and wall of the stator bore, so that a pair of chambers are formed at opposite sides of each movable vane. Opposite ends of these chambers are closed by dat end walls or caps on the stator which have a close sliding lit with at end faces on the rotor body and movable vanes.

In operation, the rotor is caused to tuin in one direction or the other, in a well known manner, by connecting the chamber at one side of each Vane to the high pressure supply of a fluid pressure system and connecting the chamber at the other side of the vane to the return line of the system. It is essential, of course, to seal the actuator against fluid leakage past the vanes and across the ends of the rotor.

In most cases a satisfactory seal at the ends of the rotor is achieved by providing a suiciently small clearance between the iiat end faces on the 'rotor and the flat mating surfaces on the stator end caps. Sealing against leakage past the vanes of .the existing rotary fluid actuators, on the other hand, is accomplished in numerous different ways.

The various vane sealing arrangements which are used on the existing actuators, however, possess one common undesirable feature. That is, in the existing actuators, the uid seals between the rotor vanes and the stator are aorded by sealing elements which are carried on the rotor and bear against the cylindrical wall of the stator bore. The iluid seals between the stator vanes and the rotor are afforded by sealing elements which are carried on the stator and bear against the cylindrical surface of the rotor. In some prior actuators, such as that disclosed in Patent No. 2,778,340, the sealing elements are the vanes themselves.

This prior sealing arrangement has several disadvantages. First, the cylindrical surfaces of both the rotor and stator are used as sealing surfaces. Both the rotor and stator, therefore, must be precision made. Also, both the surface of the rotor and the internal surface of the stator must be given a iine surface nish requiring two surface finishing operations.

Secondly, both the rotor and stator must be provided with seal slots for receiving the sealing elements. The stator seal slots are dificult to form with any degree of ,sais Patented Nov. l5, i960 A third, and perhaps the most serious disadvantage of using sealing elements whach are carried by the stator, resides in the fact that the arcs of the internal cylindric surfaces of the actuator which are exposed to high and low pressure uids vary with a change in the angular position of the rotor. This, of course, is due to the fact that the angular spacing between the stationary and movable vanes Varies as the rotor turns. This change in the arcs of the high and low pressure surfaces produces distortions of the stator housing which cause binding of the rotor, increased fluid leakage and, in general, render the prior actuators undesirably sensitive to rotor displacement or movement.

One aspect of the present invention is concerned with an improved arrangement of the vane sealing elements which cures the noted defects in the existing vane sealing arrangements. Another aspect of the invention is concerned with an improved vane sealing element which ef fects a superior sealing action.

With the foregoing preliminary discussion in mind, a broad object of this invention may be stated as being the provision of an improved rotary fluid actuator which overcomes the preliminary -noted and other deiiciencies of existing rotary fluid actuators.

A more speciiic object of the invention is the provision of a rotary fluid actuator wherein the arcs of the internal actuator sur-faces which are exposed to the high and low pressure fluids during actuator operation remain constant as the rotor turns, so as to render the present actuator relatively insensitive to rotor displacement.

Another object of the invention is the provision of a rotary uid actuatorl which is so constructed as to minimize precise machining and surface finishing operations and appreciably simplify the machining operations which are necessary.

Yet another object is the provision of a rotary fluid actuator which obvia-tes precise machining and sur-face finishing of the rotor.

Still another object is the provision of Ia rotary uid actuator which is so designed as to appreciably simplify fabrication of the stator housing.

A further object is the provision of a rotary fluid actuator wherein all of the active sealing elements are carried on and move with the rotor.

Yet a further object is the provision of an improved vane seal for a rotary fluid actuator.

A still further object is the provision of an improved rotary iluid actuator of the character described which is relatively simple in construction, designed for facility of manufacture, possesses superior operating characteristics, and is otherwise especially well suited for its intended purpose.

Other objects, advantages and features of the invention will become readily apparent as the ydescription proceeds.

Briefly, the objects of the invention are attained by the provision of a rotary fluid actuator wherein all of the active vane sealing elements are carried and tnansported by the rotor. One set of these sealing elements is contained in seal slots in the rotor vanes and slideably engage the cylindric surface of the stator bore. The other set of sealing elements is contained in seal slots in the main body of the rotor and slideably engage the cylindric surfaces on the stator vanes.

The relative positions of these sets of sealing elements remain unchanged as the rotor turns. Accordingly, the arcs lof the internal cylindric surfaces of the actuator, which lare exposed to the high and low pressure fluids during operation of the actuator, remain constant rather than varying as a function of rotor displacement, as in the existing rotary uid actuators.

Since all of the sealing surfaces, engaged by the active sealing elements of the actuator, are on the stator, the exact conguration of the rotor and the quality of its surface finish are of no consequence. Fabrication of the rotor, therefore, is greatly simplified and its cost appreciably reduced. Moreover, all of the seal slots are formed in the external surfaces of the rotor rather than in the internal surfaces of the stator, as in the existing rotary uid actuators, with the result that the seal slots may be more readily formed with greater accuracy. Also, manufacture of the stator is appreciably simplied.

The invention also provides improved vane sealing elements having vastly improved operating and sealing characteristics.

A better understanding of the invention may be had from the following detailed description, taken in connection with the Iannexed drawings, wherein:

Fig. l is a transverse section through one form of the present actuator;

Fig. 2 is a section taken along line 2 2 of Fig. l;

Fig. 3 is a transverse section through another form of the present actuator;

Fig. 4 is a partial section taken along line 4-4 of Fig. 3; and

Figs. 5 and 6 illustrate a modified form of element.

Referring now to these drawings, and more particularly to Figs. 1 and 2 illustrating a balanced rotor form of the present actuator, the numeral 201 denotes the generally cylindrical housing, or stator, of the actuator. The stator is internally congured to provide a first set of diametrically opposed internal cylindric surfaces 2.2 and a second set of diametrically opposed internal cylindric surfaces 24 having a common center on the axis 26 of the stator housing 20. The cylindric surfaces 24 are formed on a pair of diametrically opposed, radially inwardly extending projections, or vanes 28 on the stator housing 20. The cylindric surfaces 22 have the same axis as to the cylindric surfaces 24, the radius of the latter surfaces being less than the radius of the surfaces 22, as Shown.

Contained within the stator housing 210 is a rotor 30 including a generally cylindrical body 32. The diameter off the rotor body 32 is slightly less than the diameter of the cylindric surfaces 24 on the stator vanes 28 so that an annular clearance space 34 exists between the rotor body and stator vanes.

Extending radially from the rotor body 32 are a pair of diametrically opposed rotor vanes 36. The outer surfaces of these vanes are spaced from the cylindrical surfaces 22 `of the stator, as shown.

Rotor 30 is provided with two sets of diametncally opposed, axially extending seal slots 38 and 40 which are coextensive with and open through opposite ends of the rotor. Seal slots 38 are formed in the rotor vanes 36 while seal slots 40 are formed in the rotor body 32 in 90 degree spaced relationship to the seal slots 38.

In Figure 2, rotor 30 will be seen to have flat end faces 4Z spaced inwardly of the ends of the stator housing and axial shafts 44 which extend beyond the ends of the stator housing. Opposite ends of the stator housing are counterbored at 46 and internally threaded at 48. Slideably received in the counterbores 46 are end caps 50 having flat inner faces 52. These end caps are retained in the stator housing 20 by means of annular retaining nuts S4 which are threaded in the ends of the stator housing and press the end caps against outwardly facing annular shoulders 56 on the housing. O-rings 5S, contained in slots in the end caps 50, seal the latter to the stator housing 20 and the rotor shafts 44. Needle bearings 60 carried lon the end caps journal the rotor shafts 44, as shown.

As preliminarilyvmentioned, the end caps S0 serverto prevent uid leakage at opposite ends of the rotor 3u'. To this end, the length ofthe rotor 4between its end faces sealing 42 and the axial spacing between the shoulders S6 on the stator Ihousing 20 are such as to provide a so-called hydraulic clearance, on the order of .0001 inch, between each end face 42 of the rotor and the opposing at surface 52 on the adjacent end cap 50. Some lealtage, of course, will occur yat the ends of the rotor. For this reason, a leakage return passage 62, having an outlet 64, is provided in a conventional manner for returning leakage fluid to the fluid return side of the hydraulic system to which the actuator is connected. This is done to prevent the creation of a fluid pressure differential across the actuator seals 58.

Contained within each of the seal slots 38 and 40 are elastically `deformable sealing elements 66. Each of these sealing elements consists of a relatively thin walled, metal sleeve having a close, but rotatable lit in the sealed slots, The external diameter of the sealing sleeves 66, in their normal undeformed condition, is such that with the sleeves resting on the bottom of the sealed slots, the aforementioned hydraulic clearance of approximately .0001 inch will exist between the sealing sleeves and their adjacent internal cylindrical stator surfaces. The sealing sleeves 66 have llat end faces and are accurately dimensioned to have exactly the same length as the rotor between its end faces 42. The hydraulic clearance will, therefore, exist between the ends of the sealing sleeves and the at faces 52 of the stator end caps 50. In some cases, a plastically deformable sealing element, such as Teon cylinder, may be used in place of elastically deformable metal sleeves.

Accordingly, there are dened at opposite sides of each rotor vane I36 a pair of iluidly isolated chambers 68 and 70. Chambers 6g, which are diametrically opposed, are interconnected by a passage 72, the stator housing 20 having a first inlet and discharge passage 74 communicating to the chambers 68. Likewise, chambers 70, which are also d-iametrically opposed, are interconnected by `a passage '76, the stator housing having a second inlet and discharge passage 78 communicating to the chambers 70.

:It will be observed that a pair of generally quadrantshaped spaces are formed below each sealing sleeve 66. Those spaces which are adjacent the chambers 68 have been designated by the numeral 68a and those spaces which are adjacent the chambers 70 have been designated by the numeral 79a.

The rotor body 32 and rotor vanes 36 are formed with a rst set of passages 68h which communicate the chambers 68 and spaces 68a. Similarly, the rotor body and vanes have a second set of passages 7Gb which communicate the chambers 70 and spaces 70a. During operation of the actuator, therefore, the spaces 68a and 70a will be -lled with pressure fluid from the chambers 68 and 70, respectively.

In operation of the rotary iluid actuator described above, it is connected, in the usual manner, to a fluid press-ure system through suitable valving which may be operated to selectively connect the chambers 63 and 70 to the high pressure supply and the return line of the system. When this valving is operated to connect the chambers 68 to the high pressure supply and the chambers 70 to the return line, the pressure dilerential created across the rotor vanes 36 acts to turn the rotor 30 in clockwise direction. Similarly, when the valving is operated to connect the chambers 7? to a high pressure supply and the chambers 68 to the return line, the .rotor 30 is turned in a counter-clockwise direction.

Owing to the aforedescribed communication, via the passages 68h and 7Gb, lbetween the chambers 68 and 70 and the seal slot spaces 63a land 70a, it will be observed that the high pressure -fluid acts over one-half of each sealing sleeve and the low pressure fluid acts over the other half of each sleeve. This pressure differential across the four sealing sleeves 66 causes the latter to be deformed in such a way that their diameter in a radial plane of the rotor is increased. This deformation of the sealing sleeves, in turn, causes the latter to move into intimate sealing engagement with the cylindric surfaces 22 and 24 of the stator and bottom walls of the seal slots s0 as to effectively minimize fluid leakage past the sleeves from the high pressure to the low pressure chambers. Moreover, intimate sealing engagement of the sealing sleeves with the stator surfaces will be retained during expansion of the stator housing at high iiuid pressures.

The broad use of deformable sealing elements in a rotary actuator, of course, is not new. However, the Iexisting deformable sealing elements have comprised plastic-like materials having extreme cold flow characteristics. These prior deformable sealing elements, therefore, tend to be extruded, especially at high operating pressures, into the clearance space between the rotor and the stator. This, of course, results in an appreciable increase in the frictional restraint on the rotor. Moreover, these extrudable sealing elements are prone to rapid wear and deterioration and do not completely return to their initial configuration when the pressure is relieved with the result that the coetiicient of static friction of the sealing elements is appreciably increased.

ri`he present metal sleeves avoid these deficiencies since the sleeves are deformed by the pressure differential thereacross so as to be capable of maintaining effective seals at high pressures and yet do not undergo cold ow or extrusion between the rotor and stator. Also, these metal sleeves have a high degree of elasticity and return to their exact cylindrical shape when the pressure is relieved so that the static friction of the actuator is not increased. Moreover, these metal sleeves, even when deformed by pressure, are more readily rotatable in their seal slots, so as to minimize the coeiiicient of dynamic friction of the actuator, than the existing cylindrical sealing elements made from plastic-like deformable materials which are extruded, as just mentioned, under high pressures.

In this respect, it will be seen that since the high and low pressure fluids act over 180 of each sealing sleeve, the force component on each sleeve, resulting from the pressure differential thereacross, `acts normal to a radial plane of the rotor passing through the center of the sleeve. Accordingly, the pressure differentials across the sealing sleeves do not create any radial force components on the sleeves which would tend to urge the latter outwardly against the stator and thereby excessively increase the static and dynamic friction of the actuator.

One highly important advantage of containing all of the active sealing elements on the rotor, as in the present uid actuator, is that as the rotor turns the relative positions of the sealing elements, i.e., the sealing sleeves 66, remain unchanged. That is, all of the sealing sleeves are transported as a unit with the rotor as the latter turns. Accordingly, the arcs of the internal cylindric surfaces of the actuator which are exposed to the high pressure fluid remain constant. In the existing rotary fluid actuators wherein one set of sealing elements is carried on the rotor and the other set of sealing elements is carried on the stator, of course, the angular spacing between the movable and stationary elements changes as the rotor turns. Thus, as the rotor turns in one direction, the arc of the internal actuator surfaces exposed to the high pressure uid increases, and as the rotor turns in the opposite direction this arc decreases. This change in the arc of the high pressure surfaces results in undesirable non-uniform distortions of the stator housing and bending of the rotor which cause binding of the rotor, increased iiuid leakage past the actuator vanes, and, in general, render the actuator undesirably sensitive to rotor displacement or movement.

In the present rotary fluid actuator, on the other hand, the arc of the high pressure surfaces remains constant,

as just mentioned. This constancy of the arc, in eiect, results in uniform distortion of the stator housing at the higher pressures which minimizes binding of the rotor, iiuid leakage past actuator vanes, and, in general, renders the actuator relatively insensitive to rotor displacement or movement.

A second highly important advantage of containing the sealing sleeves entirely `on the rotor resides in the fact that the configuration of the rotor body and its surface texture are unimportant. That is, all of the sealing surfaces engaged by the sealing sleeves, are on the stator. The external surface of the rotor body, therefore, need not have any particular configuration or surface texture, the only requirement being that the rotor surface clear the internal cylindric surfaces of the stator. This, of course, results in a rotor which is appreciably simpler and less costly to manufacture.

A third highly important advantage of the present actuator construction is that all of the seal slots are formed in external surfaces o-f the rotor. Such external seal slots are, of course, more easily formed with greater accuracy than seal slots which are formed in internal surfaces of the stator housing, as in existing rotary iiuid actuators. The present actuator design, therefore, results in a stato-r housing which is appreciably simpler and less costly to manufacture than the stator housings of existing rotary tiuid actuators.

As shown in Figs. 3 and 4, the features of the invention may alsol be embodied in an unbalanced type rotor design. The actuator of Figs. 3 and 4 comprises a generally cylindrical stator housing 10h having a first generally semi-cylindrical internal wall 102 and a diametrically opposed, second internal semi-cylindrical Wall 104. Wall 104 is formed on a generally semi-cylindrical internal projection or vane 106 on the stator housing 100.

Contained within the housing 101i is a rotor 108 having a generally cylindrical body 110. Extending radially from one side of this body is a vane 112,A which extends axially of and is coextensive with the rotor body 110.

The rotor body 111B and rotor vane 112 are formed with axially extending seal slots 114 and 116 which are coextensive with and open through opposite ends of the rotor. Contained within these seal slots are metal sealing sleeves 11S identical to the sealing sleeves 66 in Figs. 1 and 2. These sleeves are deformable, in the same manner as the sealing sleeves 66, into sealing engagement with the internal cylindric walls 102 and 104 of the stator housing. Opposite ends of the stator housing are closed by end cap and retaining nut assemblies 120, identical to the end cap and retaining nut assemblies described with reference to Figures 1 and 2. A fluid leakage return passage 122 is provided at each end of the stator housing.

Indicated at 12a and 128 are a pair of inlet and discharge passages which open into chambers and 132 formed at opposite sides of the rotor vane 112. in operation of the actuator, these passages are connected to a fluid pressure system suitable valving, as in the case of the actuator of Figs. 1 and 2, which valving may be operated to selectively connect the chambers 13@ and 132 to the lhigh pressure supply and return line of the fluid pressure system to cause rotation or turning of the rotor w8 in one direction or the other.

In the actuator of Figures 3 and 4, the quadrantshaped seal slot spaces 13h61 and 132:1 below each sealing sleeve 11S communicate with the chambers 13G and 132, respectively, via passages 131th and 13219, respectively, for the same reasons as described with reference to the actuator of Figures 1 and 2.

It will be observed that the actuator of Figures 3 and 4, possesses the same advantages as the first described actuator of Figures l and 2. That is, the arc of the high pressure surfaces does not change with a change in rotor position, the sealing slots are formed entirely in the external surfaces of the rotor, the sealing surfaces are entirely on the stator, and the exact contiguration and surface texture of the rotor body are unimportant.

Figures and 6 illustrate a modified form of sealing element 200 which may be employed in the actuator. Sealing element 260 has a solid, semi-circular crosssect-ion, as shown. Extending radially through the element are one or more tluid passages or ports 202 which open through the flat outer face 264 and inner cylindric surface 206 of the element.

The numerals 2h53 and 2l@ denote, respectively, the rotor and stator of the actuator. These parts are substantially identical to the rotor and stator of Figure l, except that the uid leakage space or clearance C defined between the outer surfaces of the rotor vanes ZllZ (only one shown) and the inner cylindric stator surface or wall 214 is much less than in the actuator of Figure l. The modied sealing element 2% could, of course, be employed in the actuator of Figure 3.

Sealing element 26@ is loosely received in an axial seal slot 216 in the outer surface of the rotor vane 212. The flat side surface of the element, which faces outwardly of the seal slot toward the stator surface 2id, intersects the cylindric side surface of the element at opposite sides of the latter along edges 2id and 226. These edges parallel the stator surface and form sealing edges, as will shortly be seen. The depth of the seal slot is slightly less than the radius of the sealing element, and such that a clearance, which may be appreciably greater than the aforementioned hydraulic clearance, exists between the sealing edges 21S and 220 on the element and the stator wall 21d when the element seats on the bottom of the slot. The width of the slot is approximately equal to the diameter of the sealing element.

The wall of the seal slot 216 intersects the outer surface of the rotor vane 2li2, at opposite sides of the seal element, along edges 225 and 228. These edges parallel the opposing cylindric side surface of the seal element and form sealing edges, as will now be described.

During operation of the actuator, assuming chamber 222 contains the high pressure fluid and chamber 224 is connected to the return line of the duid supply system (not shown), the pressure differential across the sealing element forces the latter against the sealing edge 226 of the rotor vane. This forms a fluid seal between the element and rotor.

Fluid from the high pressure chamber leaks to the space between the sealing element, the stator wall 214i and to the seal slot space below the sealing element through the ports 2&2. Fluid leakage to these spaces also occurs through the small clearance which will exist between the sealing element and the sealing edge 228 of the rotor vane.

Fluid leakage from the high pressure chamber 222 to the low pressure chamber 22dwill also occur, at least initially, past the sealing edge 224i of the sealing element. This leakage creates a slight pressure diiferential across the sealing element which moves the edge 220 of the element into fluid sealing relationship with the stator surface 21d. The sealing element is rotated slightly by this action, as shown, and may in some cases turn to a position where the other sealing edge of the element engages the stator surface 2id.

This pressure differential is created as follows. The total head of the high pressure iiuid above and below the sealing eiement must, of course, be the same. The entire head of the fluid below the element is in the form of a pressure head. That is, the static pressure of the high pressure fluid in chamber 2.22 acts on the underside of the element.

Above the sealing element, however, a portion of the total head is in the form of a velocity head. This, of course, is due to the fluid leakage past the sealing edge 224i of the sealing element. The pressure head above the element is, therefore, reduced so that the mentioned pressure differential across the sealing element is created.

It will be apparent that the balanced position of the sealing element is approximately that illustrated. This is because any uid leakage past the seal causes the latter to assume the position shown. If, on the other hand, fluid leakage past the seal is entirely cut off, the pressure heads above and below the seal become equal. Under this latter condition, of course, no unbalanced fluid forces exist which would tend to move the seal from the illustrated position.

The above described action is reversed when chamber 224 contains the high pressure iluid, edge 218 of the seal then acting as the sealing edge.

The primary advantage of the modified seal is that the clearances between the seal, seal slot and stator wall 214.', with the actuator unpressurized, can be appreciably greater than in the case of the cylindrical seals of Figures l and 3. This permits the seal of Figures 5 and 6 to be easily axially inserted into the seal slot after insertion of the rotor in the stator. Assembly of the actuator is thus simplified.

Moreover, since the pressure differential across the seal, tending to urge the latter against the stator surface 2.14, is small, the frictional drag imposed by the seal is small. The modiiied seal is also easier to make than the cylindrical seal of Figures 1 and 3.

From what has been said above, it will be obvious that the seal need not have a semi-circular cross-section. That is, it will be observed that the essential features of the seal are that it have outer longitudinal sealing edges (218 and 22d) and a portion within the seal slot having side seal surfaces for engaging the vane sealing edges 226, 223.

It will be apparent, therefore, that there have been described and illustrated fluid actuators which are fully capable of attaining the several objects and advantages preliminarily set forth. While certain preferred embodiments of the invention have been disclosed for illustrative purposes, it will be obvious that numerous modifications in design and arrangement of parts of the invention are possible within the scope of the following claims.

I claim:

l. In a fluid pressure device having a high pressure chamber, a low pressure chamber, and a pair of approximately parallel opposing surfaces which define therebetween a iiuid leakage space between said chambers, the improvements comprising fluid sealing means to minimize fluid leakage through said space including a seal slot in one surface extending crosswise to the direction of uid leakage through the space and opening toward the other surface, a seal element loosely received in and extending the length of said slot, said element being of generally semi-circular coniguration in transverse cross-section and having its cylindric surface facing into the slot, the Wall of said slot intersect-ing said one surface at the low pressure side of said member along a first sealing edge parallel to the opposing cylindric surface of the element, said element having a second side surface which faces outwardly of said slot toward said other surface of the device and intersects said rstmentioned side surface of the element at the low pressure side of 4the latter along a second sealing edge parallel to and closely adjacent said other surface, fluid in the high pressure chamber urging said element toward said first sealing edge and said other surface to establish a iirst fluid seal between the latter edge and said opposing surface of the element and a second tluid seal between said second sealing edge and said other surface.

2. In a fluid pressure device having a pair of pressure chambers and a pair of approximately parallel surfaces which deiine therebetween a fluid leakage space between said chambers, the improvements comprising fluid sealing means to minimize fluidV leakage through said space, including a seal slot'in one surface extending crosswise to the direction of fluid leakage through said space and opening toward the other surface, a generally semicylindrical seal element loosely received in and extending the length of said slot, the cylindric surface of the element facing into the slot, the wall of said slot intersecting said one surface at opposite sides of said element along iirst sealing edges parallel to the opposing side surface of the seal element, said element having a second side surface which faces outwardly of the slot toward said other surface and intersects said first-mentioned side surface of the element at opposite sides of the latter along second sealing edges parallel to and closely adjacent said other surface, high pressure fluid in either of said chambers urging said element toward the first sealing edge remote `from the high pressure chamber and toward said other surface of the device to form a first fluid seal between the latter edge and the opposing side surface of the element and a second fluid seal between said other surface and the second sealing edge remote from the high pressure chamber.

3. The subject matter of claim 2 wherein said seal element has passage means opening through said side surfaces thereof and communicating the space between said first-mentioned side surface and the wall of the slot with the space between said second side surface and said other surface of .the device.

4. In a fluid pressure device having two pressure chambers, and a pair of opposing surfaces which define therebetween a fluid leakage space between said chambers, the improvements comprising uid sealing means to minimize iluid leakage through said space including a seal slot in one surface extending crosswise to the direction of uid leakage through the space and opening toward the other surface, a rigid seal element loosely received in said slot for limited rotational movement of the element in the slot, the side walls of said slot intersecting said one surface along first sealing edges at opposite sides of and parallel to the opposing side surface of the element which faces into the slot, said element having a second side surface which faces outwardly of said slot toward said other surface of the device and intersects said first-mentioned side surface of the element at opposite sides of the latter along second sealing edges parallel to and closely adjacent said other surface, said second side surface of the seal element being spaced Afrom said other surface of the device between said second sealing edges, a fluid pressure differential between said chambers urging said element toward the 1G low pressure chamber to establish a iirst huid seal between the first sealing edge proximate to the low pressure chamber and said opposing surface of the element and a second fluid seal between the second sealing edge proximate to the low pressure chamber and said other surface of the device.

5. In =a fluid pressure device having -a high pressure chamber, a low pressure chamber, and a pair of approximately parallel opposing surfaces which define therebetween a fluid leakage space between said chambers, the improvements comprising fluid sealing means to minimize dluid leakage through said space including a seal slot in one surface extending crosswise to the direction of fluid leakage through the space and opening toward the other surface, a seal element loosely received in and extending the length of said slot, the wall of said slot intersecting said one surface at the low pressure side of said element along a rst sealing edge parallel to the opposing side surface of the element, said element having a second side surface which faces outwardly of said slot toward said other surface of the device and intersects said first-mentioned side surface of the element at the low pressure side of the latter along a second sealing edge parallel to and closely adjacent said other surface, fluid in the high pressure chamber urging said element toward said iirst sealing edge and said other surface to establish a first fluid seal between the latter edge and said opposing surface of the element and a second fluid seal between said second sealing edge and said other surface, and said seal element having passage means opening through said side surfaces thereof and communicating the space between said first-mentioned side surface and the wall of the slot with the space between said second side surface and said other surface of the device.

References Cited in the file of this patent UNITED STATES PATENTS 1,232,850 Saunders July 10, 1917 1,887,311 Kohr Nov. 8, 1932 2,798,462 Ludwig et al. July 9, 1957 FOREIGN PATENTS 135,982 Germany Nov. 24, 1902 

